Photo-electronic multiplier 7844 (PMT-7844) – based detector is aimed for optical radiation detection in the spectral range of 185 – 900 nm. Cooled (with Peltier element) photo-electronic multiplier of H-7844 type by Hamamatsu is used as detection element in the detector. Due to use of PMT with a lateral photocathode and an embedded high-voltage power supply and active voltage divider, the detector is of small overall sizes, simple and safe in operation.